340 
Proceedings of the Royal Society 
explanations, to throw some useful light on either the proportions 
of the Great Pyramid, or the principles of that more careful men- 
suration which should be applied to it. 
General Principles of Accurate Linear Mensuration. 
In order to measure, then, any length of earth lines, in the 
accurate manner of the best base-line operations of trigonometrical 
surveys — in which I have myself, in former years, borne a practical 
part — and which are a very fair ideal of accuracy to look towards 
in Great Pyramid outside measurements, — it is necessary 
ls£, To have well-defined and fixed terminal points at either 
end of the line to be measured. 
2d, To have the ground tolerably well cleared, levelled, or 
reduced to gentle gradients, between the points. And, 
3 d, To have scientific apparatus, by which the measuring bars may 
be placed in definite linear positions, and to microscopic accuracy 
both absolutely level and parallel to the line joining the two ter- 
minal points ; under temperature circumstances, also, where the 
deviation of length of the measuring bars, from a chosen standard , 
shall be accurately computable. 
by Col. Howard Vyse, the French Academicians, Prof. Greaves, and many 
others. Wherefore arise the following questions : — 
(1.) Was the coffer really of a different length when Dr Whitman’s 
engineer visited it, than in the times of the other measurers alluded to? 
(2.) Supposing that the above was not the case, then, A, did the engineer 
officer make a mistake in his measures themselves, to the extent of 1 foot in 
6 feet ? or, B, did he, or perhaps Dr Whitman, merely misplace in his notes 
what he had measured fairly as inside measure, and place it amongst outside 
measures heedlessly ? 
I incline, now that Dr Whitman’s published numbers have been dragged 
up as being a very high authority on the coffer’s size, to choose supposition 
B as being the most probable. And then have to take for his Length inside, 
78 inches; Breadth inside, 26*75 inches; and for Depth inside, 32 inches by 
direct measure, and 35*5 if we subtract his “ thickness of stone ” from his out- 
side Height, the mean of these two being 33*75 inches. 
Deducing these values from British inches to Pyramid inches, we have 
77*92 x 26*72 x 33*72 = 70,206 Pyramid cubic inches, where the alleged 
14,000 inches of difference are reduced to nearly 1000 inches; and even that 
is chiefly chargeable on evident rudeness and mistakes in the Depth measure; 
for the true quantity (say 34*31) is included within the two very wide 
determinations given. 
